Apparatus and procedure for the drawing of films in motion

ABSTRACT

This invention relates to an apparatus ( 1 ) for the transversal drawing of a film ( 2 ) in motion, comprising a pair of rollers ( 3, 4 ) rotating on parallel axes, fitted with toothed surface profiles ( 5, 6 ) capable of compentrating without touching each other and defining a wavy passage ( 7 ) for the film, where the rounded tips of the toothed profiles ( 5, 6 ) of the two rollers ( 3  and  4 ) define the points of application of the drawing action on the film ( 2 ).

[0001] The object of this invention is an apparatus for the drawing of films in motion, at least in a direction perpendicular to the direction of motion of the film, also known as a Cross Direction Orientator.

[0002] The further object of this invention is a procedure for the drawing of films in motion, at least in a direction perpendicular to the direction of motion of the film.

[0003] For various applications, for instance in the hygienic article trade, there is an ever growing demand for transpiring plastic films.

[0004] The drawing of the film may be carried out in the direction of the forward motion of the film and/or in the direction perpendicular to the direction of the forward motion of the film.

[0005] Various types of apparatus are currently known, capable of performing the transversal or longitudinal drawing of a film in motion.

[0006] On the other hand, the known types of apparatus exhibit various drawbacks and a generally poor reliability, considerable encumbrance and high production cost.

[0007] The purpose of this invention is to offer an apparatus for the transversal drawing of film materials in motion, capable of eliminating at least part of the drawbacks provided by the devices of a known art.

[0008] One possible embodiment of the drawing apparatus will now be described for purely exemplifying and non-limiting purposes, under reference to the attached drawings in which:

[0009]FIG. 1 offers a simplified view of an apparatus in accordance with the statements in the claims,

[0010]FIG. 2 shows a enlarged detail of the apparatus, showing a film material before entering into the passage between the transversal drawing rollers, and

[0011]FIG. 3 offers a view of the same enlarged detail that shows the film material while entering the passage between the two drawing rollers and in the process of drawing.

[0012] With reference to the attached drawings, the number 1 indicates in the overall an apparatus for the drawing of the materials of film 2 in motion, which comprises a pair of rotating rollers 3 and 4, having prallel axes, with surperficially toothed profiles 5 and 6 compenetrating but not touching each other while outlining, in their compenetrating area, a wavy passage 7 through which then film is passed.

[0013] When entering this wavy pssage 7, the film 2 comes in contact with the rounded ends of the toothed profiles 5 and 6 and of the rollers 3 and 4— which define the applicative points of a progressive transversal drawing morion with respect to the direction of forward motion of the film 2 (refer to FIG. 3).

[0014] The rollers 3 and 4 are obviously rotating in the same direction of forward motion of the film 2, preferably at a speed slightly higher than that of the film itself, so as to keep the film in a slight tension.

[0015] In another possible embodiment the speed of the rollers 3 and 4 can be considerably higher than that of film 2, so as to also subject the film 2 to an appreciable drawing action in a longitudinal sense (meaning in the direction of the forward motion of the film 2).

[0016] The rollers 3 and/or 4 will also preferably be fitted with devices capable of regulating the surface temperature of the profiles 5 and 6, so as to facilitate the drawing action.

[0017] Alternatively it will be possible to provide the use of devices designed to heat the film before contacting the toothed profiles 5 and 6.

[0018] Such devices are known to an expert in the trade, and are therefore not to be described further.

[0019] While using the drawing apparatus on some polyolefine films the surface temperature may attain about 80° C., depending on the composition of the material, its speed and the desired drawing ratio.

[0020] The shape and sze of the teeth may vary depending on the desired drawing ratio.

[0021] It is obviously important that the toothed profiles 5 and 6 do not present irregularities or sharp edges, which would cause the film itself to tear. 

1. An apparatus (1) for the transversal drawing of a film (2) in motion, comprising a pair of rollers (3, 4) rotating on parallel axes, fitted with toothed surface profiles (5, 6) capable of compentrating without touching each other and defining a wavy passage (7) for the film, where the rounded tips of the toothed profiles (5, 6) of the two rollers (3 and 4) define the points of application of the drawing action on the film (2).
 2. An apparatus according to claim 1 , providing some devices capable of regulating the angular speed of said rotating rollers (3, 4).
 3. An apparatus according to claim 2 , where the surface temperature of said rotaing rollers (3, 4) is adjustable between 20 and 80° C.
 4. An apparatus according to claim 2 , also comprising some devices to heat the film, (2), within a temperature between 20 and 80° C., before it comes in contact with the toothed profiles (5, 6).
 5. A procedure for drawing a polyolefine film in motion, comprising a phase of passing the film across a wavy passage (7) in a transversal sense (2) with respect to the direction of forward motion of the film (2), so as to subject the film to a multiple number of transverse stretching actions, distributed over its entire width.
 6. An apparatus according to claim 5 , where said wavy passage is constituted by two rotaing rollers rollers (3, 4) equipped with a toothed profile.
 7. An apparatus according to claim 6 , where said rotating rollers (3, 4) rotate at a peripheral velocity exceeding that of the of the film (2).
 8. A procedure according to claim 5 , wherein the film is heated to a temperature held between 20 and 30°X. 